JP2005340959A - Optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission system improving a transmission efficiency by solving nonuniformities among nodes required for setting an optical path. <P>SOLUTION: A node-hop number control unit 18 is fitted, and the number of node hops at every label switch path is controlled. The optical paths are generated preferentially from the label switch paths having a more number of the node hops. That is, an optical-path set requirement acceptance time is defined, and the optical paths are set by preferring the LSP having the most number of passing nodes in optical-path set requirement messages brought during that time. Consequently, probabilities are improved in which the optical paths are formed to the nodes having a large number of hops, and the delay time of the whole network can be shortened. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical transmission system including a plurality of optical node devices and formed by overlaying on a packet communication network or the like. This type of system is also called a photonic network or an all-optical network.

  Advances in Internet technology are fast. The traffic flowing through the communication network was mainly fixed telephone traffic in the early 1990s, but now most of it is data traffic flowing through the Internet. With the explosive spread of the Internet and broadband, the metro and trunk line traffic that supports the Internet is also increasing rapidly. From this background, the traffic that can be accommodated in the existing communication network is approaching its limit.

  On the other hand, research and development on photonic networks are actively conducted. The photonic network is also called an all-optical network, and is a system that transmits an optical signal as it is without being converted into an electrical signal in a node. Since no optical / electrical conversion processing or packet header interpretation is required, the transmission efficiency of the photonic network is higher than that of the existing network.

  Therefore, in recent years, a technique has been studied in which a photonic network having an optical cross-connect as a node is overlaid on an existing network, and traffic that cannot be accommodated in the existing network is transferred to the photonic network (also referred to as cut-through). (For example, refer to Patent Document 1 and Non-Patent Document 1). The traffic of the existing network is accommodated in the optical path set in the photonic network. Setting the optical path temporarily as needed can reduce the initial investment in the photonic network than setting the optical path fixedly. In particular, in Non-Patent Document 1, the cost of the system is reduced by limiting the number of optical transceivers provided in each node.

In this type of system, MPLS (Multi-Protocol Label Switching) standardized by IETF (Internet Engineering Task Force) is used to set an optical path in a photonic network. In recent years, GMPLS (Generalized MPLS), which is an extension of this, is often used. In addition, label distribution protocol (LDP) and RSVP (Resource Reservation Protocol) used for resource reservation are known. By interpreting “label” as “wavelength”, these protocols can be used for optical path setting processing.
JP 2002-016950 A IEICE 2003 Society Conference B-6-140

  By the way, in the optical path setting process using the above protocol, the optical path setting request message is transferred on the hop-by-hop route of the default wavelength λ0 and arrives at the start point (ingress) node of the optical path. At this time, in the current system, the first-come-first-served processing is performed at the start point node that has received the optical path setting request. That is, the control packet for the optical path setting request may arrive at the starting node from a node far away or may arrive from a nearby node.

  In a situation where there is a lot of traffic on the existing network, an optical path setting request is issued every time an optical path is released, but requests from nodes far from the start node are always slower than requests from nearby nodes. Therefore, an optical path setting request from a node close to the start point node is always prioritized.

  Since the optical path is cut through through the optical matrix switch, the effect of using the optical path is greater as the number of nodes on the way increases. However, if the priority of the optical path setting varies depending on the distance, the merit of cut-through of the data packet is canceled, and a transmission delay is caused.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical transmission system that eliminates inequality between nodes related to optical path setting, thereby improving transmission efficiency.

  In order to achieve the above object, according to one aspect of the present invention, there is provided an optical transmission system that is overlaid on a packet communication network including a plurality of routing nodes that switch a packet transferred on a label switch path. When the generation request is given from the packet communication network, the node hop number calculating means for calculating the number of node hops of the label switch path designated by the optical path generation request, and the node hop number calculating means There is provided an optical transmission system comprising optical path generation means for generating an optical path capable of accommodating at least a part of the traffic in preference to a label switch path having a large number of node hops.

  By taking such means, the number of node hops is managed for each label switch path, and an optical path is generated preferentially from label switch paths with a large number of node hops. As a result, the optical path generation process is not performed in the order of arrival of messages, and inequality between nodes related to optical path setting can be eliminated. Therefore, it is possible to improve the transmission efficiency by averaging the delay times.

  ADVANTAGE OF THE INVENTION According to this invention, the inequality between the nodes concerning an optical path setting can be eliminated, and the optical transmission system which aimed at the improvement of the transmission efficiency by this can be provided.

  FIG. 1 is a system diagram showing an embodiment of an optical transmission system according to the present invention. The system of FIG. 1 includes a plurality of nodes 103 (103-1 to 103-5). Each of the nodes 103-1 to 103-5 includes a label switch router (LSR) 101 (101-1 to 101-5) and a photonic cross connect (PXC) 102 (102-1 to 102-5). .

  The nodes 103-1 to 103-5 are appropriately connected via the optical transmission lines 104-1 to 104-6. Each of the optical transmission lines 104-1 to 104-6 is composed of a plurality of wavelength-multiplexed optical links, and one of the wavelengths λ0 is a default wavelength, and the nodes are connected hop-by-hop. That is, the wavelength λ0 is always subjected to photoelectric conversion for each node, and electrical processing of the signal is performed. The wavelength λ0 is used for transmission of network control signals and L2 / L3 layer packets. The packet passing through the L2 / L3 layer is switched by the label switch router 101 of the node that has passed through until reaching the destination.

  In the plane indicated as the L2 / L3 layer in FIG. 1, dotted arrows connecting the LSRs indicate that the nodes are logically mesh-connected. The logical route that connects each node to the mesh is called a label switch path (LSP). The mesh connection is only logical, and in practice, packets passing through this network proceed through the LSP while being switched hop-by-hop by LSR.

  The LSR has a function of measuring traffic of an LSP passing through its own node. When each node 103-1 to 103-5 detects that the traffic of a certain LSP has increased, it cuts through the traffic of that LSP at the L1 layer. Specifically, an L1 layer optical path passing through the PXC is set along the route through which the LSP passes, and the LSP traffic is transferred to the optical path.

  The PXC has a function of connecting light of an arbitrary wavelength input to an arbitrary input port to an arbitrary output port without converting the light into an electric signal and without performing wavelength conversion. Therefore, the optical path starts from the start point node, passes through several PXCs without being wavelength-converted, and reaches the end point node.

  In FIG. 1, for example, when an LSP that connects LSRs 101-1 and 101-3 is cut through in the L1 layer, it is assumed that the LPS physically passes through LSRs 101-1, 101-2, and 101-3. . If an optical path setting request is made to the nodes 103-1, 103-2, and 103-3 and the request is accepted by satisfying the conditions such as the wavelength, the optical paths that pass through the PXCs 102-1, 102-2, and 102-3 105 is set. Note that the node that issues the optical path setting request is any one of the nodes 103-1, 103-2, and 103-3.

  When the optical path 105 is successfully set, the node 103-1 directs the LSP traffic that is stretched toward the LSR 101-3 input to the LSR 101-1 toward the PXC 102-1, and the node 103-3 is transmitted by the optical path 105. To reach. The node 103-3 directs the traffic of the optical path 105 reaching the PXC 102-3 to the LSR 101-3. In this way, the node 103-2 is cut through and the load on the LSR 101-2 is reduced.

  In the existing system having the network architecture of FIG. 1, after a certain time has elapsed after the optical path is established, the optical path is forcibly released regardless of the traffic in the optical path. Therefore, after the optical path is released, if there is still a lot of traffic in the corresponding LSP, an optical path setting request is generated again.

  Packets traveling on the LSP are switched each time they pass through the LSR. The LSR queues the input packet in the buffer of the corresponding output port by store and forward. If the buffer is empty, the packet will immediately go out of the LSR, but if there are other packets in the buffer, they will not be output until the turn comes. On the other hand, since the PXC only connects the input and the output as a line, a packet traveling on the optical path almost passes through the PXC. Accordingly, the delay performance is clearly different between the case where packets of the same destination pass through the LSP and the case where they pass through the optical path.

  In this type of system, a new optical path setting request after the optical path is released is accepted on a first-come-first-served basis. Each node issues an optical path setting request when the traffic flowing through the LSP exceeds a specific threshold. The optical path setting request is transferred on a hop-by-hop route with the default wavelength λ0 and arrives at the optical path start point node. The optical path start point node that has received the optical path setting request processes the received optical path setting request in the order of arrival. The control packet for the optical path setting request may arrive from a distant node or may arrive from a nearby node.

  In a situation where there is a lot of traffic, after the optical path is released, immediately after the data traffic returns to the original LSP, an optical path setup request is forwarded to the node that released the optical path. A request from a node far from the optical path start point node is always slower than a request from a nearby node. Therefore, priority is given to an optical path setting request from a node close to the optical path start point node.

  The optical path is cut through by the optical matrix switch for the passing node. Therefore, the larger the number of nodes on the optical path, the greater the effect of using the optical path. However, if priority is given to the optical path between the nodes close to the optical path starting point node, the merit of transferring data packets to the optical path is reduced. In the following, an embodiment of the present invention capable of solving such problems is disclosed.

[First Embodiment]
FIG. 2 is a functional block diagram showing an embodiment of the node 103 in FIG. The node 103 in FIG. 2 includes a label switch router 101 and a photonic cross connect 102. The photonic cross connect 102 includes an optical matrix switch 11, a wavelength multiplexing MUX / DMUX 12, and an optical matrix switch control unit 20. In order to simplify the description in FIG. 2, the optical matrix switch 11 is assumed to be an optical space matrix switch having 10 ports for input and 10 ports for output. The wavelength division multiplexing MUX / DMUX 12 can multiplex and multiplex a total of three wavelengths λ0, λ1, and λ2, and among these, λ0 is a default wavelength. The optical matrix switch 11 has a function of selecting an arbitrary port within the same wavelength. For convenience of explanation, the number of wavelengths is set to 3, but the number of wavelengths is not limited. The photonic cross connect 102 is connected to different nodes via the optical transmission path 104.

  The optical signal of the default wavelength λ0 input / output from the wavelength multiplexing MUX / DMUX 12 is converted into an electrical signal by the default optical transceiver unit 13 of the label switch router 101. The converted electrical signal is switched to the corresponding output port in the label switch function unit 14 based on the label information included in the electrical signal. Normally, the electric signal input / output to / from the label switch function unit 14 is packet data composed of a header portion and variable length data. Since a fixed-length label is added to the packet data, it is called a labeled packet. In order for the labeled packet to select and switch an appropriate output port by the label switch function unit, it is necessary to refer to the label table indicating the relationship between the label value and the output port. The router unit 16 has a function of creating this label table.

  The router unit 16 has a function of a normal IP (Internet Protocol) router and a label table creation function. When the node 103 operates as an edge device of the network, the router unit 16 is connected to an external network such as an IP network. That is, the router unit 16 has a function of transmitting and receiving IP packets with the IP network. Adjacent nodes are connected by default wavelength λ0.

  The label switch function unit 14 adds a default label to the IP packet from the router unit 16 and forwards it to the adjacent node. The label switch function unit 14 to which the default label is input always drops the label, returns it to the IP packet form, and inputs it to the router unit 16. The network formed in this way can behave as an IP router network connected hop-by-hop at the time of startup.

  With this mechanism, the router unit 16 can operate a dynamic routing protocol such as OSPF (Open Shortest Path First). The router unit 16 can automatically create a forwarding table using a dynamic routing protocol. By looking at the destination IP address of the IP packet input to the router unit 16 from the external network, the default label corresponding to the next hop node can be selected.

  Similar to the above-described external IP packet transfer mechanism, a label table creation function inside the router unit 16 (not shown) and an IP packet for control input / output from the optical path setup / release control unit 17 It is possible to communicate with the label table creation function and the optical path setting / release control unit of all the nodes.

  In this system, after completion of the forwarding table, a full mesh label switch path (LSP) between nodes is set. In order to create a label table, it is necessary to perform LSP signaling for connection. For LSP signaling, the MPLS technique is used. In MPLS, a path request message is sent from a start node of an LSP to a downstream node, and a label value is determined hop-by-hop using a reserve message from the end point node of the LSP to the start point node. create. At this time, the number of passing nodes can be counted. Therefore, the start node of the LSP that has received the reserve message can store the number of node hops as an attribute in the node hop count management unit 18 together with the LSP identifier.

  The traffic measuring unit 19 has a function of measuring the amount of data traffic measured by the label switch function unit 14. Specifically, in the label switch function unit 14, a buffer queue may be provided for each LSP, and the traffic measurement unit 19 may monitor the amount of data held in the queue. There is no problem even if the data traffic volume is measured using other methods.

  When the LSP is stretched to a full mesh, a packet passing through the node 103 is input to the label switch function unit 14 via the default optical transceiver unit 13, but is turned back here and is connected to the adjacent node via the default optical transceiver unit 13. Forwarded to In this situation, when data traffic exceeding a preset threshold is observed by the traffic measuring unit 19, a trigger for an optical path setting request is generated toward the optical path setting / release control unit 17. Upon receiving the trigger, the optical path setup / release control unit 17 sends an optical path setup request message toward the start node of the corresponding LSP. The optical path setup request message is converted into a labeled packet by the label switch function unit 14 via the router unit 16, converted into an optical signal of λ0 by the default optical transceiver unit 13, and is transmitted hop-by-hop by the start node of the LSP. Arrives at the optical path setting / release control unit 17.

  Upon receiving the optical path setup request message, the optical path setup / release control unit 17 of the start node of the LSP starts a timer that measures a predetermined reception time. Also, based on the LSP identifier, the number of passing nodes of the LSP is read. Assume that the optical path setup / release control unit 17 receives an optical path setup request message again while the timer does not reach the acceptance time. The number of transit nodes of the LSP is read from the identifier of the LSP for the optical path setting request message received second. Compare the number of transit nodes read first, and select the larger one. This is repeated within the reception time, and when the timer exceeds the reception time, the timer is reset and an optical path request message is sent from the optical path setup / release control unit 17 toward the end point node of the LSP.

  Regarding this part of signaling, standardization work is being performed as GMPLS (Generalized MPLS), which is a more general extension of MPLS. Although details are omitted, the optical path setup / release control unit 17 of the optical path end point node that has received the optical path request message returns the optical path reserve message to the start point node, and the light of the node through which the optical path passes and the light of the start point node. The optical matrix switch 11 is switched via the matrix switch control unit 20. At the start node of the optical path, the wavelength of the wavelength tunable transceiver unit 15 is set to the wavelength determined by the GMPLS mechanism, and the data that has flowed through the LSP is transferred via the wavelength tunable transceiver unit 15. This switching can be realized by changing the label table or by changing the label value. Since the optical matrix switch 11 is set in the middle node of the optical path and passes through the optical signal as it is, the delay time of the data packet is determined only by the light passing time. As described above, each node 103 monitors the traffic of the LSP which is the default path, and starts the optical path setting procedure when detecting a state to be transferred to the optical path (traffic has increased beyond a threshold). .

  In the above configuration, the optical path setting / release control unit 17, the optical matrix switch control unit 20, and the optical matrix switch 11 generate an optical path that can accommodate at least a part of the traffic of the default path. The optical path setting / release control unit 17, the optical matrix switch control unit 20, and the optical matrix switch 11 determine the lifetime of the optical path for each default path, and schedule the release time of the optical path based on the lifetime. Since the optical matrix switch 11 is set in the middle node of the optical path and passes through the optical signal as it is, the delay time of the data packet is determined only by the time through which the light passes.

  The optical path setup / release control unit 17 includes a timer (not shown) for measuring the optical path lifetime, and the optical path setup / release control unit 17 outputs an optical path release message toward the optical path end point node. Thus, the optical path whose survival time has been exceeded is released. At the start node of the optical path, the data transferred through the wavelength tunable transceiver unit 15 is returned to the LSP through the default optical transceiver unit 13.

  When the traffic load of the entire network is large, a situation occurs in which an optical path setup request message arrives at the node immediately after the optical path lifetime is exceeded and the optical path is released. If the optical path is set in the order of arrival of the optical path setting request message, the message from the node close to that node arrives early in the optical path setting request message. Therefore, the probability that the optical path is set for a distant node is low.

  Therefore, in this embodiment, a node hop number management unit 18 is provided to manage the number of node hops for each label switch path. Then, an optical path is generated preferentially from label switch paths having a large number of node hops. That is, by defining an optical path setup request reception time and setting an optical path with priority given to the LSP with the largest number of passing nodes in the optical path setup request message arriving in the meantime, a node with a large number of hops Therefore, the probability that an optical path is established is increased, and the delay time of the entire network can be reduced.

  Further, in the present embodiment, after the optical path is set, an optical path release delay timer (not shown) is started after a predetermined lifetime has elapsed by the optical path lifetime timer of the optical path setup / release controller 17. The activation trigger of the optical path release grace timer is when the optical path lifetime has elapsed or when the data traffic observed by the traffic measuring unit 19 becomes zero.

  The optical path start point node does not release the optical path while the optical path release grace timer has not reached the predetermined release grace time. Within that time, if there is again an optical path that has exceeded the optical path lifetime or an optical path for which data traffic has become zero, the number of node hops managed by the node hop number management unit 18 Leave few LSPs as candidates. The number of node hops is compared until the optical path release grace time ends.

  As described above, when setting an optical path, priority is given to an optical path with a large number of node hops, and when releasing an optical path, an optical path with a large number of node hops remains. As a result, the probability that an optical path having a large number of node hops is established as an optical path is increased, and the delay time of the entire network is reduced.

  As described above, in the present embodiment, the label switch router having the default optical transceiver unit 13 that transmits and receives an optical signal having a common wavelength in all nodes and the plurality of wavelength variable transceiver units 15 that can vary the wavelength other than the common wavelength. Assume a network in which a plurality of nodes 103 including 101 and a photonic cross-connect 102 are mesh-connected. Then, the control packet is transmitted and received between the label switch routers 101 using the default optical transceiver unit 13. Using this control packet, the full mesh label switch path between the nodes 103 is set. At this time, the amount of traffic flowing through the label switch path is measured at each node 103. A label switch path whose measured traffic volume exceeds a preset traffic threshold is accommodated in the optical path. The optical path is released after a specified time. In an all-optical network performing the above operation, when an optical path setting request is made, a label switch path having a large number of node hops among the corresponding label switch paths is preferentially accommodated.

  As the number of node hops in the label switch path, the number of hops is stored as an attribute of the label switch path when setting the label switch path so that the nodes are fully meshed. Furthermore, the number of hops of the label switch path is written in the optical path setting request message, and this number of hops is read at the start node (ingress) of the optical path.

  Further, when the optical path start point node receives the optical path setting request message at the time of the optical path setting request, the optical path setting request is received during a predetermined receiving time, and a plurality of arrivals within the receiving time are received. In the optical path setting request message, the label switch path with the largest number of hops is accommodated in the optical path.

  Further, after the optical path is established after the optical path has been set, the start node of the optical path does not immediately release the optical path for a predetermined release grace period, and the optical path is not exceeded within the release grace period. Among a plurality of optical paths that have exceeded the lifetime, an optical path that accommodates a label switch path with the smallest number of hops is preferentially released. The relationship between the LSP identifier and the number of node hops is stored at the stage where the full mesh LSP is established, and when a plurality of optical path setting requests arrive within a specific time, an LSP with a large number of node hops is preferentially made an optical path Accommodate. Thereby, since the optical path is not delayed in the middle node, the delay of the entire optical network can be reduced.

  As described above, according to this embodiment, it is possible to prevent a situation in which an optical path having a small number of intermediate nodes between the start node and the end node of the optical path is always prioritized. Since the optical path cuts through the nodes, if the LSP having a large number of intermediate nodes is accommodated in the optical path, the performance of the entire network is improved and a network with a low delay can be realized. When setting an optical path, priority is given to an LSP with a large number of hops, and priority is given to a label switch path with a small number of hops, so that the entire network can realize a low-latency network.

[Second Embodiment]
FIG. 3 is a functional block diagram showing a second embodiment of the node 103 in FIG. Parts common to FIG. 2 are denoted by the same reference numerals, and only different parts will be described here. In the system of FIG. 1, after completion of the forwarding table, a full mesh label switch path (hereinafter abbreviated as LSP) between nodes is set. In order to create a label table, it is necessary to perform LSP signaling for connection. For LSP signaling, the MPLS technique is used. Briefly, a path request message is sent from the start point node of the LSP to the downstream node, and the label value is determined hop-by-hop using the reserve message from the end point node of the LSP to the start point node. Then, create a label table.

  At the stage where the LSP is stretched to the full mesh, the packet passing through the node is input to the label switch function unit 14 via the default optical transceiver unit 13 of FIG. To the adjacent node. In this situation, the delay time measurement packet is sent from the optical path setup / release control unit 17 at the LSP start node to the optical path setup / release control unit 17 at the LSP end node. In the delay time measurement packet, the time when the packet was created is written as a time stamp. This packet is transferred on the LSP in the same manner as user data.

  The optical path setup / release control unit 17 of the LSP end point node passes the difference between the current time and the time stamp to the packet delay measurement unit 21 as the LSP delay time. The packet delay measurement unit 21 compares the LSP delay time with a preset threshold value. When the LSP delay time exceeds the threshold, the packet delay measurement unit 21 generates a trigger for an optical path setting request to the optical path setting / release control unit 17. Upon receiving the trigger, the optical path setup / release control unit 17 sends an optical path setup request message in which the LSP delay time is written to the start node of the corresponding LSP. The optical path setup request message is converted into a labeled packet by the label switch function unit 14 via the router unit 16, converted into an optical signal of λ0 by the default optical transceiver unit 13, and is transmitted hop-by-hop by the start node of the LSP. Arrives at the optical path setting / release control unit 17.

  Upon receiving the optical path setup request message, the optical path setup / release control unit 17 of the LSP start point node starts a timer for measuring a predetermined reception time. Further, the LSP delay time is read from the optical path setup request message together with the LSP identifier, and stored in the delay time comparison unit 22 together with the LSP identifier. Assume that the optical path setup / release control unit 17 receives an optical path setup request message again while the timer does not reach the acceptance time. Next, the optical path setup / release control unit 17 reads the LSP delay time written in the second received optical path setup request message. Then, the first read LSP delay time is compared with the second value, and the larger one is selected. This is repeated within the reception time, and when the timer exceeds the reception time, the timer is reset, and an optical path request message is sent from the optical path setup / release control unit 17 toward the end point node of the LSP.

  This part of signaling is controlled by GMPLS. The optical path setup / release control unit 17 of the optical path end point node that has received the optical path request message returns the optical path reserve message to the start point node, and passes through the optical matrix switch control unit 20 of the node through which the optical path passes and the start point node. Then, the optical matrix switch 11 is switched. At the start node of the optical path, the wavelength of the wavelength tunable transceiver unit 15 is set to the wavelength determined by the GMPLS mechanism, and the data that has flowed through the LSP is transferred via the wavelength tunable transceiver unit 15. This switching can be realized by changing the label table or by changing the label value.

  As described above, in this embodiment, the packet delay time flowing on the LSP is directly measured, and the optical path is set with priority on the LSP having a large packet delay time. Even with such a method, the entire network can be reduced in delay as in the first embodiment.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a system diagram showing an embodiment of an optical transmission system according to the present invention. The functional block diagram which shows 1st Embodiment of the node 103 of FIG. The functional block diagram which shows 2nd Embodiment of the node 103 of FIG.

Explanation of symbols

  101 (101-1 to 101-5) ... label switch router, 102 (102-1 to 102-5) ... photonic cross-connect (PXC), 103 (103-1 to 103-5) ... node, 104 ... light Transmission path, 105 ... optical path, 11 ... optical matrix switch, 12 ... wavelength multiplexed MUX / DMUX, 13 ... default optical transceiver section, 14 ... label switch function section, 15 ... wavelength variable transceiver section, 16 ... router section, 17 ... Optical path setting / release control unit, 18 ... Node hop number management unit, 19 ... Traffic measurement unit, 20 ... Optical matrix switch control unit, 21 ... Packet delay measurement unit, 22 ... Delay time comparison unit

Claims (7)

An optical transmission system overlaid on a packet communication network comprising a plurality of routing nodes for switching packets transferred on a label switch path,
A node hop number calculating means for calculating the number of node hops of the label switch path designated by the optical path generation request when an optical path generation request is given from the packet communication network;
An optical path generating means for generating an optical path capable of accommodating at least a part of the traffic in preference to a label switch path having a large number of node hops calculated by the node hop count calculating means. Optical transmission system. The number of node hops is an attribute that is stored for each label switch path when setting a label switch path so that a full mesh connection is established between nodes, and is described in an optical path setting request. The optical transmission system according to 1. The optical path generation means generates an optical path for accommodating the traffic of the label switch path having the largest calculated value of the number of node hops within a specified period when a plurality of optical path setting requests compete. The optical transmission system according to claim 1. The optical path releasing means for releasing an optical path accommodating a label switch path with the smallest number of node hops among the scheduled optical paths that have reached the release time. Optical transmission system. An optical transmission system overlaid on a packet communication network comprising a plurality of routing nodes for switching packets transferred on a label switch path,
When an optical path generation request is given from the packet communication network, node hop number calculation means for calculating a packet delay amount of the label switch path specified by the optical path generation request;
An optical path generating means for generating an optical path capable of accommodating at least a part of the traffic in preference to a label switch path having a large packet delay calculated by the node hop count calculating means. Optical transmission system. 6. The optical transmission system according to claim 5, wherein the packet delay amount is an attribute described in the optical path setting request. The optical path generation means generates an optical path for accommodating the traffic of the label switch path having the largest calculated packet delay amount within a specified period when a plurality of optical path setting requests compete. The optical transmission system according to claim 5.

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